Presently on the market, there are different types of contaminated air vent systems allowing, notably, to discharge contaminated air from certain domestic apparatuses towards the outside of buildings. In general, these systems comprise, at their outlet, a pivoting valve closing the opening of this outlet such that the penetration of the air coming from the outside and which is generally caused by wind gusts is reduced. However, these valves are not very efficacious. The air penetration into the ducts then causes the loss of thermic energy, particularly during cold weather. Moreover, also in cold weather, the heat loss towards the exterior caused by conduction around a vent system with a pivoting valve is only slightly reduced.
Therefore, there is a need for an air vent system having the object of not only discharging contaminated air towards the exterior, but also to substantially reduce the penetration of outside air in the ducts due to the wind gusts in the ducts, and to reduce the heat loss due to conduction towards the exterior of the ducts during cold weather.